<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        /* 不要使用下划线_, 使用-来隔开 */
        /* 见名知意 */
      c-orange {
          color: orange;
      }
    </style>
</head>
<body>
    <div class="c-orange">
        猥琐发育，别浪
    </div>
    <div>全军出击</div>
    <div>哎呀，被玩坏了</div>
</body>
</html>